Facile and Efficient Method for the Prins Reactions of Styrenes and Homoallyl Alcohols to 1,3‐Dioxanes and 4‐Tetrahydropyranols Using Bismuth(III) Triflate

Abstract

Bismuth(III) triflate has been found to be an efficient catalyst for the Prins reactions of styrenes and homoallyl alcohols, the reaction proceeds rapidly and affords the corresponding 1,3‐dioxanes and tetrahydropyran‐4‐ol in good yields. Scope and limitations of the styrenes and homoallyl alcohols are reported.     

Novel Route to Functionalized Indans via Formal [3 + 2] Cycloadditions of 1-Benzylbenzotriazoles with Alkenes

α-Functionalized 1-benzylbenzotriazoles (3, 4 and 12), derived from the lithiation of 1-(2,3-dimethoxybenzyl)benzotriazole 2 followed by reactions with electrophiles, or from the condensation of benzyl alcohol 11 with benzotriazole, undergo formal [3 + 2] cycloadditions with styrenes upon treatment with ZnBr₂ to give functionalized indans (9, 10, 13 and 14).     

A simple Lewis acid induced reaction of phenols with electrophiles: Synthesis of functionalized 4H-chromenes and ortho-benzylphenols

Abstract

Lewis acid ZnCl₂ promoted cyclization protocol to 4H-chromenes is accomplished, using readily available phenols and acetophenones as starting materials. Interestingly, the process is feasible under the solvent free environment. Synthesis of a variety of 4H-chromenes have been accomplished using this strategy. In addition, this concept is extended to the synthesis of ortho-benzylphenols by treating phenols either with styrenes or secondary benzylic alcohols.     

KHSO4: a highly efficient and reusable heterogeneous catalyst for hydroarylation of styrenes

Abstract  

Hydroarylation of styrenes with arenes/heteroarenes using KHSO₄ (10 mol%) as an efficient heterogeneous catalyst is described. High conversion and selectivity (>99%) were observed for hydroarylation of styrenes with 2-naphthol at reflux temperature of 1,2-dichloroethane. Yields were quantitative with all styrenes. Moderate to good conversions and selectivities were achieved with other aromatics and heteroaromatics under the same conditions. Regeneration and reusability of KHSO₄ were demonstrated. Addition of a trace amount of water could help to reactivate the KHSO₄ through dispersion and to facilitate the hydroarylation reaction.     

Spontaneous reactions of electron‐accepting substituted quinodimethane with substituted styrenes: Inductive and steric effects on the formation of a zwitterionic intermediate

Spontaneous reactions of an electron‐accepting substituted quinodimethane, 1‐(2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione‐5‐ylidene)‐4‐(dicyanomethylene)‐2,5‐cyclohexadiene, with p‐substituted, α‐substituted, and β‐substituted styrenes were investigated. When p‐substituted styrenes were used as comonomers, no spontaneous reactions took place for styrenes with an electron‐accepting p substituent such as COOMe and CN groups, and both terpolymers and cycloadducts were formed for the other p‐substituted styrenes. When α‐substituted and β‐substituted styrenes were used as comonomers, no reactions occurred for α‐ and β‐substituted styrenes with a bulky phenyl group, and spontaneous reactions took place for those with a smaller methyl group. The reaction products were an alternating copolymer for α‐substituted styrene and both terpolymers and 5‐ethylidene‐2,5‐dimethyl‐1,3‐dioxane‐4,6‐dione for β‐substituted styrenes. The position of the methyl group in the styrenes significantly affected the product formation. This behavior in the spontaneous reactions was discussed on the basis of the ability of formation of the zwitterionic tetramethylene intermediate and its conformation, determined by polar and steric effects of the substituents in the substituted styrenes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5195–5206, 2005     

Rh(I)-Catalyzed Asymmetric Hydrosilylation and Hydroboration/Oxidation Reactions Using Berens Ligand

The Berens ligand 2 was used in a number of Rh(I)-catalyzed asymmetric hydrosilylations of acetophenones under standard conditions, affording the corresponding 1-arylalcohols in ees up to 65%. Some novel Rh catalysts were generated in situ from the neutral precatalyst [Rh(µ-Cl)(COD)]₂ and screened in the catalytic asymmetric hydroboration/oxidation of styrenes, gave enantioselectivities of up to 62%.     

A NEW ROUTE FOR THE SYNTHESIS OF STYRYLBENZYLSULFONES,PRECURSORS OF 1-BENZYLSULFONYL-2-ARYLCYCLOPROPANES

Abstract

A novel method for the synthesis of E-styrylbenzylsulfones from E-sodium styrysulfinates and benzyl chlorides has been described. The cyclopropanation of these compounds with dimethylsulfonium methylide gave E-1-benzylsulfonyl-2-arylcyclopropanes in good yields. The corresponding Z-isomers have been obtained by the cycloaddition of benzylthiocarbenes to styrenes under phase transfer catalysis. Their geometry has been assigned based on IR and ¹H NMR spectral data.     

Catalytic olefination reaction of carbonyl compounds. A study on stereoselectivity of alkene formation

The mechanism of formation of alkene stereoisomers in the catalytic olefination reaction of carbonyl compounds was studied. 4-Chlorobenzaldehyde hydrazone 1 stereoselectively reacts with a number of F-, Cl-, Br-, and I-containing polyhaloalkanes in the presence of catalytic amounts of CuCl to give -substituted styrenes 2 with the more thermodynamically stable alkene isomer being the major product. A model for the formation of the stereoisomers of alkenes 2 in the olefination reaction is proposed. Stereoselectivity of the reaction is determined by elimination of copper(ii) halides from the lowest-lying conformers of organocopper intermediates II. According to quantum-chemical calculations, the elimination should involve the staggered conformations with antiperiplanar arrangement of C—Hal and C—Cu bonds and proceed by the E2 anti-elimination mechanism. The results of quantum-chemical calculations are in good agreement with the experimental E/Z alkene isomer ratios.     

New data on the reaction of hexafluorothioacetone with styrenes

Hexafluorothioacetone, generated in situ from its cyclic dimer (1) in the presence of CsF catalyst was shown to react with styrene or 4-alkyl-styrenes (alkyl = c-hexyl, Me, t-Bu) forming the corresponding 2:1 Diels-Alder cycloadducts as major products. All cycloadducts were isolated, and the structure of two of them was established by single crystal X-ray diffraction. While 2-vinylnaphthalene, 4-CF₃- and 4-Cl-styrenes in the presence of CsF catalyst react with 1 producing the corresponding 1:1 Diels-Alder cycloadducts, 4-alkoxy styrenes were found to produce preferentially the corresponding thietanes. The reaction of styrenes with 1 was also found to be sensitive to the source of fluoride ion and the solvent.     

Novel efficient synthesis of β-fluoro-β-(trifluoromethyl)styrenes

CF₃CFBr₂ was employed in catalytic olefination reactions of aromatic aldehydes. In situ prepared hydrazones of aldehydes were transformed to β-fluoro-β-(trifluoromethyl)styrenes by reaction with CF₃CFBr₂ under CuCl catalysis. Based on this reaction, a novel stereoselective approach towards β-fluoro-β-(trifluoromethyl)styrenes was elaborated. Nucleophilic vinylic substitution of fluorine by secondary amines, thiolates and alkoxides in β-fluoro-β-(trifluoromethyl)styrenes was also tested.     

Synthesis of Axially Chiral Styrenes through Pd-Catalyzed Asymmetric C−H Olefination Enabled by an Amino Amide Transient Directing Group

The atroposelective synthesis of axially chiral styrenes remains a formidable challenge due to their relatively lower rotational barriers compared to the biaryl atropoisomers. Herein, we describe the construction of axially chiral styrenes through Pd^II-catalyzed atroposelective C−H olefination, using a bulky amino amide as a transient chiral auxiliary. Various axially chiral styrenes were produced with good yields and high enantioselectivity (up to 95 % yield and 99 % ee). Carboxylic acid derivatives of the resulting axially chiral styrenes showed superior enantiocontrol over the biaryl counterparts in Co^III-catalyzed enantioselective C(sp³)−H amidation of thioamide. Mechanistic studies suggest that C−H cleavage is the enantioselectivity-determining step.     

Synthese,eigenschaften und carbonyl-insertions-reaktionen von tetracarbonyleisen(0)-komplexen para-substituierter styrole

The Fe(CO)₄ η²-complexes of para-substituted styrenes (substituent  H, CH₃, OCH₃, Cl, F) can be obtained in good yields. Complexation changes drastically the chemical shifts and coupling constants of the vinyl protons. Reaction of the complexes with one mole equivalent of bromine in methanol liberates styrenes, but using two equivalents esters and diesters are formed via intermediate complexes of iron(III). For these carbonyl insertion reactions no systematic influence of the substituent on yield and product distribution was observed.     

Synthesis of Axially Chiral Styrenes through Pd‐Catalyzed Asymmetric C−H Olefination Enabled by an Amino Amide Transient Directing Group

The atroposelective synthesis of axially chiral styrenes remains a formidable challenge due to their relatively lower rotational barriers compared to the biaryl atropoisomers. Herein, we describe the construction of axially chiral styrenes through Pd^II‐catalyzed atroposelective C?H olefination, using a bulky amino amide as a transient chiral auxiliary. Various axially chiral styrenes were produced with good yields and high enantioselectivity (up to 95 % yield and 99 % ee). Carboxylic acid derivatives of the resulting axially chiral styrenes showed superior enantiocontrol over the biaryl counterparts in Co^III‐catalyzed enantioselective C(sp³)?H amidation of thioamide. Mechanistic studies suggest that C?H cleavage is the enantioselectivity‐determining step.     

Cerium(IV) ammonium nitrate: Reagent for the versatile oxidative functionalization of styrenes using N-hydroxyphthalimide

Cerium(IV) ammonium nitrate was found to be a versatile reagent for the oxidative functionalization of styrenes using N-hydroxyphthalimide and iodine affording three different types of products with oxyphthalimide, nitrate and iodide groups. It was shown that reaction of styrenes with N-hydroxyphthalimide and cerium(IV) ammonium nitrate can be selectively directed to oxynitro-oxyphthalimides and dioxyphthalimides depending on the reaction conditions, in particular a solvent. Reaction of styrenes with iodine under the action of N-hydroxyphthalimide and cerium(IV) ammonium nitrate leads to the formation of iodo-oxyphthalimides.     

Styrene Aziridination by Iron(IV) Nitrides

Thermolysis of the iron(IV) nitride complex [PhB(tBuIm)₃Fe?N] with styrene leads to formation of the high‐spin iron(II) aziridino complex [PhB(tBuIm)₃Fe‐N(CH₂CHPh)]. Similar aziridination occurs with both electron‐rich and electron‐poor styrenes, while bulky styrenes hinder the reaction. The aziridino complex [PhB(tBuIm)₃Fe‐N(CH₂CHPh)] acts as a nitride synthon, reacting with electron‐poor styrenes to generate their corresponding aziridino complexes, that is, aziridine cross‐metathesis. Reaction of [PhB(tBuIm)₃Fe‐N(CH₂CHPh)] with Me₃SiCl releases the N‐functionalized aziridine Me₃SiN(CH₂CHPh) while simultaneously generating [PhB(tBuIm)₃FeCl]. This closes a synthetic cycle for styrene azirdination by a nitride complex. While the less hindered iron(IV) nitride complex [PhB(MesIm)₃Fe?N] reacts with styrenes below room temperature, only bulky styrenes lead to tractable aziridino products.     

A Novel Method for Preparation of 2‐Chloro Enesulfonamides

A novel method for the synthesis of 2‐chloro enesulfonamides via the one‐pot addition‐elimination of N ‐chloro‐N ‐fluorobenzenesulfonamides (CFBSA ) to styrenes in the presence of Et₃N is described. A total of 20 examples are presented to illustrate this concept including various of styrenes.     

Selective initiation of nonconjugated dienes containing electron donor–electron acceptor systems. III. Synthesis of vinyl ether–styrene monomers

In a continuation of our studies on nonconjugated dienes containing electron donor–electron acceptor systems which may function as model crosslinking monomers, we here report the synthesis of the series, 2-, 3-, and 4-(2-vinyloxyethoxy)styrenes. The dipole moments μ, infrared and ultraviolet absorption properties, refractive indices n_D³⁰, molar refractions (MR_D), and optical exaltations of the compounds were determined. In order to establish whether any intramolecular electronic interactions, e.g., intramolecular charge-transfer complexes, contribute to the structure and properties of these compounds, 2- and 4-(2-ethoxyethoxy)styrenes were also prepared, and their properties compared with those of the vinyloxy series. While there are differences in certain of the properties of these two groups of monomers, these differences are not sufficiently large to permit definite correlations with the proposed interactions.     

Aerobic photo-oxidative cleavage of the C-C double bonds of styrenes

Carbon tetrabromide enables us to carry out oxidative cleavage of the C-C double bonds of styrenes under aerobic photo-irradiation conditions. Oxidative cleavage of the various β-substituted styrenes produced benzoic acid in good yields. Since this reaction is found to be applicable to the α- or β-substituted styrenes, which showed very low reactivity under our previous cleavage reaction condition with FSM-16 and I₂, this reaction can be used complementarily.     

Asymmetric epoxidation of styrenes catalyzed by molybdenum complexes with amino alcohol ligands

Two common amino alcohols, prolinol and isolucinol, and their derivatives have been screened to coordinate with MoO₂(acac)₂ to form in situ catalysts for asymmetric epoxidation of styrenes with the highest enantioselectivity of 84% for 4-fluoro-styrene under the optimized reaction conditions.     

New synthetic methods for 2,3-diarylacridin-9(10H)-one and (E)-2-aryl-4-styrylfuro[3,2-c]quinoline derivatives

Two new synthetic methodologies for 2,3-diarylacridin-9(10H)-ones were developed. The first one involves the Heck reaction of (E)-3-iodo-2-styrylquinolin-4(1H)-ones with styrenes, leading to (E,E)-2,3-distyrylquinolin-4(1H)-ones, which when heated at high temperatures cyclize in two different ways. Electrocyclization and further in situ oxidation leads to 2,3-diarylacridin-9(10H)-ones, while tautomerization, cyclization by nucleophilic addition and further in situ oxidation produces (E)-2-aryl-4-styrylfuro[3,2-c]quinolines as the main compound. The second method gives only 2,3-diaryl-10-methylacridin-9(10H)-ones and involves the Heck reaction of (E)-3-iodo-1-methyl-2-styrylquinolin-4(1H)-ones and styrenes, leading to (E,E)-1-methyl-2,3-distyrylquinolin-4(1H)-ones, which when heated at high temperatures cyclize through electrocyclization and oxidation processes affording the expected compounds. The structures of all new compounds were established by extensive NMR studies.